Magnetic head including spin valve element with first to third terminals in which first current flows between the second terminal and the third terminal, and second current flows to the first terminal and is lower than the first current, magnetic recording and reproducing apparatus, and method of manufacturing magnetic head

ABSTRACT

A magnetic head according to an embodiment includes: a spin valve element with three terminals including a nonmagnetic base layer, a first terminal including a first magnetic layer, a second terminal including a second magnetic layer, and a third terminal including a third magnetic layer; and a slider including a first external lead terminal connecting to the first terminal, a second external lead terminal connecting to the second terminal, and a third external lead terminal connecting to the third terminal, in an operation, a first current being caused to flow from the second external lead terminal to the third terminal via the second terminal and the nonmagnetic base layer, and a second current that is lower than the first current being caused to flow to the first terminal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2014-203327 filed on Oct. 1, 2014in Japan, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a magnetic head, amagnetic recording and reproducing apparatus, and a method ofmanufacturing a magnetic head.

BACKGROUND

At present, signals recorded in a hard disk drive is read by detecting,by a magnetic sensor, a leakage magnetic field from recording bitswritten in a magnetic disk.

However, as the recording density has been improved, the size of arecording bit has become very small, on the order of about 10 nm. Forthis reason, compatibility between the downsizing of magnetic sensorsand the improvement in sensitivity thereof has become indispensable. Inparticular, as the gap length between magnetic shields in a reader hasbecome very narrow, the thickness of magnetic sensor has been desired tobe 10 nm or less.

However, spin valve elements commonly used at present have a four-layerstructure including a magnetization free layer, a nonmagneticintermediate layer, a synthetic, magnetization pinned layer, and anantiferromagnetic layer. Since the antiferromagnetic layer for pinningthe magnetization of the magnetization pinned layer requires a thicknessof about 10 nm to have satisfactory magnetization-pinningcharacteristics in the magnetization pinned layer, it is not easy toreduce the entire thickness of the four-layer structure to 20 nm orless.

Spin valve elements have been attracting attention, since they may serveas thin magnetic sensors capable of being disposed in a 10-nm gapbetween magnetic shields.

However, as will be described later, the spin valve elements aredifficult to be used in hard disk heads that read data from hard diskdevices (HDDs; magnetic recording and reproducing apparatuses) with finebits, difficult to be downsized, and easy to be affected by externalfactors. Furthermore, the reported spin valve elements detect therecording magnetic field of media using variations in electrochemicalpotential, which is caused by the spin accumulation, as an electromotiveforce by means of a voltmeter having infinite internal resistance. Thus,it is difficult to perform the detection with preamplifiers ofcurrently-available HDDs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a common spin valve element.

FIG. 2 is a diagram showing an example of electrochemical potentialdistributions of up-spin electrons and down-spin electrons in a commonspin valve element.

FIGS. 3A and 3B are diagrams each showing an example of electrochemicalpotential distributions along a path of a nonmagnetic base electrode ina common spin valve element.

FIG. 4 is a cross-sectional view showing an example of a hard disk headincluding a common spin valve element.

FIG. 5 is a diagram showing examples of electrochemical potentialdistributions each with a different length between a spin injectionmagnetic member and a ground position of a nonmagnetic base electrode ina common spin valve element.

FIG. 6 is a diagram for explaining a required size of a common spinvalve element.

FIG. 7 is a diagram showing an example of a spin valve element, to whichexternal lead terminals are connected.

FIG. 8 is a diagram showing examples of electrochemical potentialdistributions, in cases where an external lead terminal is present andnot present on the spin injection magnetic member side.

FIG. 9 is a diagram showing examples of electrochemical potentialdistributions, in cases where an external lead terminal is present andnot present on the spin injection magnetic member side.

FIG. 10 is a diagram showing an example of a three-terminal, spin valveelement of a magnetic head according to the first embodiment.

FIG. 11 is a diagram showing an example of electrochemical potentialdistributions along paths of up-spin electrons and down-spin electronsin the three-terminal spin valve element according to the firstembodiment.

FIG. 12 is a diagram showing electrochemical potential distributionsalong the center line of nonmagnetic base layer of the three-terminalspin valve element according to the first embodiment.

FIGS. 13A and 13B are diagrams showing examples of electrochemicalpotential distributions along the path of the three-terminal spin valveelement according to the first embodiment.

FIG. 14 is a plan view showing an example of the nonmagnetic base layerand the magnetic layers according to the first embodiment.

FIG. 15 is a plan view showing another example of the nonmagnetic baselayer and the magnetic layers according to the first embodiment.

FIG. 16 is a plan view showing the three-terminal spin valve elementaccording to the first embodiment when viewed from the ABS.

FIG. 17 is a diagram showing the relationship between the ratio betweenthe junction area of the common terminal and the junction area of thespin detection terminal and the normalized output, obtained by asimulation.

FIG. 18 is a diagram showing the relationship between the arealresistance RA of the high-resistance interface layer of the free layerand the CT width of the free layer, and the areal resistance RA of thefree layer.

FIGS. 19A to 19D are cross-sectional views showing a process of formingthe nonmagnetic base layer, the spin injection terminal, the commonterminal, and the spin detection terminal according to the firstembodiment.

FIG. 20 is a diagram showing an example of a three-terminal spin valveelement according to a modification of the first embodiment.

FIG. 21 is a cross-sectional view showing a hard disk head according tothe second embodiment.

FIG. 22 is a cross-sectional view showing a hard disk head according toa modification of the second embodiment.

FIG. 23 is a cross-sectional view showing a hard disk head according toExample 1.

FIG. 24 is a cross-sectional view showing a hard disk head according toExample 2.

FIG. 25 is a cross-sectional view showing a hard disk head according toExample 3.

FIG. 26 is a cross-sectional view showing a hard disk head according toExample 4.

FIG. 27 is a cross-sectional view showing a hard disk head according toComparative Example 1.

FIG. 28 is a cross-sectional view showing a hard disk head according toComparative Example 2.

FIG. 29 is a cross-sectional view of a three-terminal spin valve elementaccording to Comparative Example 3.

FIG. 30 is a cross-sectional view showing a three-terminal spin valveelement according to Comparative Example 4.

FIG. 31 is a perspective view showing the structure of a magneticrecording and reproducing apparatus according to the third embodiment.

FIG. 32 is a perspective view showing a head stack assembly.

FIG. 33 is an exploded perspective view showing a head stack assembly.

FIG. 34 is a diagram showing an external lead terminal attached to aslider.

DETAILED DESCRIPTION

A magnetic head according to an embodiment includes: a three-terminalspin valve element including a nonmagnetic base layer, a first terminalincluding a first magnetic layer, in which a direction of magnetizationis switchable, the first terminal connecting to a portion near one ofopposing end faces of the nonmagnetic base layer in a direction alongwhich the nonmagnetic base layer extends, a second terminal including asecond magnetic layer, in which a direction of magnetization is pinned,the second terminal connecting to the nonmagnetic base layer so as to beat a distance from the first terminal along the direction in which thenonmagnetic base layer extends, and a third terminal including a thirdmagnetic layer, in which a direction of magnetization is pinned to beantiparallel to the direction of magnetization of the second magneticlayer, the third terminal connecting to the nonmagnetic base layer so asto be at distances from the first terminal and the second terminal alongthe direction in which the nonmagnetic base layer extends; and a sliderincluding a first external lead terminal connecting to the firstterminal, a second external lead terminal connecting to the secondterminal, and a third external lead terminal connecting to the thirdterminal, in an operation, a first current being caused to flow from thesecond external lead terminal to the third terminal via the secondterminal and the nonmagnetic base layer, and a second current that islower than the first current being caused to flow to the first terminal.

Before embodiments are described, how the embodiments are reached willbe described.

FIG. 1 is a schematic diagram of a common spin valve element. This spinvalve element has a structure in which a spin injection magnetic member210 and a spin detection magnetic member 220 are electrically connectedto a nonmagnetic base electrode 200. A current source is connectedbetween the spin injection magnetic member 210 and a terminal of thenonmagnetic base electrode 200, and a sense current flows therethrough.A voltmeter is connected between the spin detection magnetic member 220and the other terminal of the nonmagnetic base electrode 200 to measurea voltage therebetween. In such a common spin valve element, a lead 230is connected to the other terminal of the nonmagnetic base electrode200, and the other terminal of the nonmagnetic base electrode 200 isconnected to the voltmeter via the lead 230.

A sense current is caused to flow between the nonmagnetic base electrode200 and the spin injection magnetic member 210. Since the electricresistance in a magnetic material differs between majority spinelectrons and minority spin electrons, a spin-polarized current flowsthrough the nonmagnetic base electrode 200, and the electrochemicalpotential of conduction electrons in the nonmagnetic base electrode 200differs between up-spin electrons and down-spin electrons.

FIG. 2 shows an example of up-spin electron electrochemical potential μ↑and down-spin electron electrochemical potential μ↓ plotted along thecenter line of the nonmagnetic base electrode 200. The lateral axis inFIG. 2 indicates distance along the nonmagnetic base electrode 200 froma point of origin on the nonmagnetic base electrode 200, and thelongitudinal axis indicates electrochemical potential.

In this example, 0V is applied to the nonmagnetic base electrode 200,and a positive voltage is applied to the spin injection electrode 210.Accordingly, both an up-spin current I↑ and a down-spin current I↓ flowfrom the spin injection electrode 210 to the nonmagnetic base electrode200. The difference in electrochemical potential (μ↑−μ↓) caused therebyhas a maximum value at an interface with the spin injection electrode,and relaxed toward zero as the distance therefrom increases.Hereinafter, the difference in electrochemical potential (μ↑−μ↓) is alsoreferred to as “spin accumulation.” The spin accumulation isexponentially relaxed with respect to the distance so that theelectrochemical potential μ↑ of the up-spin electrons and theelectrochemical potential μ↓ of the down-spin electrons have the samevalue. The distance at which the spin accumulation is relaxed to 1/e(where e is the base of the natural logarithm) is called “spinrelaxation length λn.” This value is a material property value, andvaries depending on the material for forming the nonmagnetic baseelectrode 200.

Differential values of electrochemical potential are proportional to thecurrent of spin electrons in respective directions. From FIG. 2, it canbe understood that the gradient of μ↑ and the gradient of μ↓ areopposite to each other after the position of the spin injectionelectrode 210. Thus, it can be understood that the up-spin current I↑and the down-spin current I↓ flow in opposite directions. Therefore, thesum of these currents (=I↑+I↓) becomes zero, and no current flows at anyposition located after the spin injection electrode 210 in the positivedirection. However, a spin current defined as I↑−I↓ flows. This currentis called “pure spin current.”

The spin detection magnetic member 220 is electrically in contact withthe nonmagnetic base electrode 200. Since the spin relaxation length λfin a magnetic material is generally very short, about a few nm to 10 nm,the up-spin electrons and the down-spin electrons are short-circuited inthe magnetic material, and rapidly relaxed. Therefore, if theelectrochemical potential distribution in the nonmagnetic base electrode200 is as shown in FIG. 2, down-spin electrons flow into the spindetection magnetic member 220, and up-spin electrons flow therefrom.

At this time, the value of majority carrier specific resistance ρ⁺ ofthe spin detection magnetic member 220 differs from the value ofminority carrier specific resistance ρ⁻ thereof. Accordingly, thevoltage at which the electrochemical potentials in the spin detectionmagnetic member 220 are relaxed (the voltage at which μ↑=μ↓) differsbetween a case where the magnetization of the spin injection magneticmember 210 and the magnetization of the spin detection magnetic member220 are parallel to each other and a case where they are antiparallel toeach other.

FIGS. 3A and 3B show examples of electrochemical potential distributionsalong a path from the spin detection magnetic member 220 to thenonmagnetic base electrode 200 in the cases where the magnetizations ofthe magnetic material 210 and the magnetization of the magnetic material220 are parallel to each other and antiparallel to each other. Thepotential difference between the spin detection magnetic member 220 andthe nonmagnetic base electrode 200 is the difference in electrochemicalpotential between the left end and the right end in each of FIGS. 3A and3B. It can be understood that the sign of the difference in the casewhere the magnetizations are parallel is opposite to that in the casewhere the magnetizations are antiparallel. Therefore, whether the twomagnetizations are parallel or antiparallel to each other can bemeasured by measuring the voltage.

If the magnetizations of the two magnetic materials 210, 220 make anangle θ with each other, the potential difference therebetween isV=(Vp+Vap)/2−Vs/2·cos θ where the potential difference in the parallelcase is Vp, the potential difference in the antiparallel case is Vap,and the difference therebetween is Vap−Vp=Vs. Therefore, the relativeangle between the magnetizations of the two magnetic materials can bemeasured by measuring the potential difference. If, for example, one ofthe magnetic material forms a pinned layer (magnetization pinned layer),in which the magnetization is pinned by an antiferromagnetic material,and the other magnetic material forms a free layer (magnetization freelayer), in which the magnetization is switched by an external magneticfield, a so-called spin vale structure can be obtained. This can be usedas a magnetic sensor of a hard disk head or the like.

FIG. 4 shows an example of a hard disk head structure using a non localspin valve element. The spin valve element includes a first multilayerstructure including a spin injection layer 210 of a magnetic material,an antiferromagnetic material 240, and a lead layer 250 stacked on anonmagnetic base electrode 200 in this order, a second multilayerstructure including a spin detection layer 220 of a magnetic material, aconductive layer 270 a, and an upper magnetic shield 260 stacked in thisorder on the nonmagnetic base electrode 200, and a third multilayerstructure including a conductive layer 270 b and a lower magnetic shield280 stacked in this order on the nonmagnetic base electrode 200. Thefirst multilayer structure and the second multilayer structure arearranged on the same side of the nonmagnetic base electrode 200 so as tobe separated from each other, and the third multilayer structure isarranged on an opposite side of the nonmagnetic base electrode 200 tothe second multilayer structure. A sense current is caused to flowbetween the nonmagnetic base electrode 200 and the lead layer 250, and avoltage between the upper magnetic shield 260 and the lower magneticshield 280 is measured. The distance between the upper magnetic shield260 and the lower magnetic shield 280 is regarded as a gap therebetween.The end faces of the upper magnetic shield 260, the conductive layer 270a, the spin detection layer 220, the nonmagnetic base electrode 200, theconductive layer 270 b, and the lower magnetic shield 280 are on thesame plane. These end faces form an air bearing surface (ABS).

As compared to a common spin valve element having a multilayer structureincluding a magnetic material, a nonmagnetic material, a magneticmaterial, and an antiferromagnetic material, the total thickness of thespin valve element shown in FIG. 4 is thinner since the spin injectionlayer 210 and the spin detection layer 220 can be arranged laterally. Ifthe spin valve element shown in FIG. 4 is used as a magnetic sensor in ahard disk head, only the free layer and the nonmagnetic base electrodeare required to be exposed at the ABS. For this reason, the thicknesscan be reduced by the thicknesses of the antiferromagnetic material andthe magnetization pinned layer. Accordingly, the distance (gap) betweenthe shields can be reduced, and a hard disk head having a higher linearresolution can be provided.

As described above, a spin valve element utilizes a feature that thereis a difference between values of μ↑ and μ↓ due to the spin accumulationin a nonmagnetic base electrode. Therefore, the greater the spinaccumulation in the nonmagnetic base electrode at the interface with thespin detection magnetic member is, the higher the detection outputbecomes. Accordingly, the spin relaxation length of the nonmagnetic baseelectrode is preferably as long as possible, and the distance betweenthe spin injection magnetic member and the spin detection magneticmember is preferably as short as possible.

As a result of a detailed study of the junction between the spininjection magnetic member and the nonmagnetic base electrode, it isfound, with respect to the electrochemical potential in the nonmagneticbase electrode, that if the ground position (where the external leadterminal is connected) of the nonmagnetic base electrode is at adistance of about the spin relaxation length λn from the junction, ahigher spin accumulation can be obtained since the spin accumulation isnot relaxed until the distance from the junction between the spininjection magnetic member and the nonmagnetic base electrode reachesabout the spin relaxation length λn. If there is a heterogeneousstructure such as a junction to an external lead terminal or a materialhaving a shorter spin relaxation length at a distance that is shorterthan the spin relaxation length λn, the spin relaxation may beaccelerated thereby, and the spin accumulation may be reduced.

FIG. 5 shows examples of electrochemical potential distributions incases where the distance between the spin injection magnetic member andthe ground position (where an external lead terminal is connected) ofthe nonmagnetic base electrode is varied. As can be understood from FIG.5, the spin accumulation becomes greater if the aforementioned distancebecomes longer to about the spin relaxation length λn.

Furthermore, as a result of a detailed study of the junction between thespin detection magnetic member and the nonmagnetic base electrode, it isfound that the ground position (where an external lead terminal isconnected) is preferably located at a distance of a few times the spinrelaxation length λn from the junction between the spin injectionmagnetic member and the nonmagnetic base electrode since the spinaccumulation is not relaxed before the position at a distance of a fewtimes the spin relaxation length λn from the junction between the spininjection magnetic member and the nonmagnetic base electrode, and thespin accumulation does not become μ↑=μ↓. If there is a heterogeneousstructure such as a junction to an external lead terminal or a materialhaving a shorter spin relaxation length at a distance that is shorterthan such a length, the spin accumulation may be reduced, and noises maybe caused.

As described above, the dimensions of the spin injection magnetic memberand the spin detection magnetic member of a spin valve element can besatisfactorily reduced so as to be in a rectangular shape having, forexample, a width of 10 nm, a length of 10 nm, and a thickness of 5 nm tobe used for a high-density hard disk head. However, even in such a case,the nonmagnetic base electrode 200 should have a length sufficientlylonger than the spin relaxation length λn. As shown in FIG. 6, theentire length of the spin valve element should be a few μm.

For this reason, the freedom in design is limited, and heterogeneity ordefects may arise in somewhere in the nonmagnetic base electrode havinga length of a few μm. If a contact to an external lead terminal isprovided within the length of a few μm, such a contact exerts aninfluence to the spin accumulation, and the element tends to receivedisturbance such as degradation of output characteristics, and becomeshard to manufacture.

In order to describe the aforementioned feature in more detail, astructure in which external lead terminals 290 a, 290 b are located nearthe spin injection magnetic material 210 and the spin detection magneticmember 220 as shown in FIG. 7 is studied.

FIG. 8 shows examples of electrochemical potential distributions incases where the external lead terminal 290 a is located near the spininjection magnetic member 210 and where it is not located near the spininjection magnetic member 210. As can be understood from FIG. 8, whenthe external lead terminal 290 a is located near the spin injectionmagnetic member 210, the spin accumulation is reduced.

FIG. 9 shows examples of electrochemical potential distribution forcases where the external lead terminal 290 b is located near the spindetection magnetic member 220 and where it is not located near the spindetection magnetic member 220. As can be understood from FIG. 9, whenthe external lead terminal 290 b is located near the spin detectionmagnetic member 220, the spin accumulation is reduced.

Thus, it is found that a common spin valve element tends to be subjectedto the influence of disturbance, such as the degradation of outputcharacteristics caused by the position of connecting external leadterminals.

Furthermore, since the above described common spin valve element has afour-terminal structure, four external lead terminals are needed. Thismeans that the number of terminals is twice that of conventionaltwo-terminal spin valve elements. This causes a problem in that drawingout a terminal from a spin valve element located at an ABS of a head isdifficult. In the case of the two-terminal element, the upper and lowermagnetic shields can be used as external lead terminals. Therefore, themanufacture of such elements is relatively easy. However, afour-terminal element requires two additional external lead terminals.Therefore, the process to manufacture such elements becomes complicated,which leads to the degradation of yield, and the increase in costs.

In order to deal with this problem, JP 2012-234602A discloses athree-terminal spin valve element. The structure proposed in JP2012-234602A includes a common terminal serving as both a terminal forapplying a current on the nonmagnetic base electrode side and a terminalfor detecting a voltage on the nonmagnetic base electrode side, by whicha three-terminal structure is achieved.

However, in order to have a sufficient spin accumulation in thenonmagnetic base electrode by this method, the position of the commonterminal should be located at a distance of a few times the spinrelaxation length λn from the spin injection magnetic member and thespin detection magnetic member. Therefore, the size of the nonmagneticbase electrode is needed to be increased to about a few μm. Accordingly,the problems that the freedom of design of the element is limited, andthe element tends to be subjected to external disturbance are noteliminated. Furthermore, since the length of the nonmagnetic baseelectrode should be increased, the element resistance is increased, andthe signal-to-noise ratio is degraded. Moreover, since the length of thenonmagnetic base electrode should be increased, and a sense current witha large current density should be caused to flow therethrough, thepossibility of the occurrence of such problems as an increase intemperature and electromigration is increased.

The present inventors have studied hard to obtain a three-terminal spinvalve element which can be used in a hard disk head for reading datafrom a hard disk drive with minute recording bits, and is capable ofreducing the size and unlikely to be affected by external environment.Some embodiments of such a three-terminal spin valve element will bedescribed below with reference to the accompanying drawings.

First Embodiment

FIG. 10 shows a magnetic head (hard disk head) according to the firstembodiment. The magnetic head according to the first embodiment includesa three-terminal spin valve element including a nonmagnetic base layer(nonmagnetic base electrode) 10, and a spin injection terminal 12, acommon terminal 14, and a spin detection terminal 16 arranged to beseparated from each other on the nonmagnetic base layer 10 along thedirection in which the nonmagnetic base layer 10 extends. Each of thespin injection terminal 12, the common terminal 14, and the spindetection terminal 16 includes a magnetic layer. In the firstembodiment, the common terminal 14 is located between the spin injectionterminal 12 and the spin detection terminal 16. Furthermore, the spininjection terminal 12, the common terminal 14, and the spin detectionterminal 16 are located on a face on the same side of the nonmagneticbase layer 10. Incidentally, the spin injection terminal 12 and thecommon terminal 14 are located within a distance that is satisfactorilyshorter than the spin relaxation length λn of the nonmagnetic baseelectrode 10. Interface layers 352, 354, 356 each with a high resistanceare disposed between the nonmagnetic base layer 10 and the respectivemagnetic terminals.

The spin injection terminal 12 includes a magnetic layer in which thedirection of magnetization is pinned. The common terminal 14 includes amagnetic layer (pinned layer) in which the direction of magnetization ispinned. The direction of magnetization in this magnetic layer isantiparallel to the direction of magnetization in the magnetic layer ofthe spin injection terminal 12. The spin detection terminal 16 includesa magnetic layer (free layer), in which the direction of magnetizationis switchable. This means that the direction of magnetization can bechanged in accordance with an external magnetic field.

The magnetic layers of the spin injection terminal 12 and the commonterminal 14 are connected to external lead terminals P1, P2 of a sliderof a magnetic head (hard disk head), which will be described later,respectively. The external lead terminals P1, P2 are further connectedto a current source 30 of a preamplifier 300, so that a sense currentflows therethrough. The magnetic layer of the spin detection terminal 16is connected to an external lead terminal P3 of the slider. The externallead terminal P3 of the spin detection terminal 16 and the external leadterminal P2 of the common terminal 14 are further connected to aresistance 31 of the preamplifier 300, and the voltage between theexternal lead terminals P2, P3 is measured by a voltmeter 32. Thus, thespin valve element according to the first embodiment has athree-terminal structure in which the common terminal 14 is shared inthe preamplifier 300. The preamplifier 300 includes the current source30 and the resistance 31. In FIG. 10, the ABS (Air Bearing Surface) is aface facing a magnetic recording medium when the three-terminal spinvalve element 1 according to the first embodiment is used as themagnetic sensor of the magnetic head. DT (Down Track) is a direction inwhich the magnetic recording medium moves, and SH (Stripe Height) is adirection toward the magnetic recording medium.

A sense current flows through the nonmagnetic base electrode 10 via thespin injection terminal 12 and the common terminal 14. The sense currententers through the magnetic layer of one of the above two terminals, andexits through the magnetic layer of the other. A spin-polarized currentflows through the nonmagnetic base electrode 10 at this time since theelectric resistance in the magnetic layer differs between majority spinelectrons and minority spin electrons. The electrochemical potential ofconduction electrons in the nonmagnetic base electrode 10 differsbetween up-spin electrons and down-spin electrons.

FIG. 11 shows the plotting of electrochemical potentials μ↑, μ↓ ofup-spin electrons and down-spin electrons along the path of the sensecurrent. In this example, the voltage of the magnetic layer of thecommon terminal 14 is set at 0 V, and the voltage of the magnetic layerof the spin injection terminal 12 is set at a positive voltage. The pathof the sense current shown in FIG. 11 is from the top face (theconnection face between the external lead terminal P1 and the spininjection terminal 12) through the spin injection terminal 12, a firstjunction face at which the spin injection terminal is connected to thenonmagnetic base electrode 10, the nonmagnetic base electrode 10, asecond junction face at which the common terminal 14 is connected to thenonmagnetic base electrode 10, the common terminal 14, and the top faceof the common terminal 14 (the connection face between the commonterminal 14 and the external lead terminal P2). Therefore, both theup-spin current I↑ and the down-spin current I↓ flow from the spininjection terminal 12 to the nonmagnetic base electrode 10, and thenfrom the nonmagnetic base electrode 10 to the common terminal 14.

In the first embodiment, the magnetization direction of the magneticlayer of the spin injection terminal 12 and the magnetization directionof the magnetic layer of the common terminal 14 are antiparallel to eachother. Accordingly, spin accumulation for increasing the up-spin currentμ↑ occurs at both the first junction face between the spin injectionterminal 12 and the nonmagnetic base electrode 10 and the secondjunction face between the common terminal 14 and the nonmagnetic baseelectrode 10. Furthermore, since the distance between the spin injectionterminal 12 and the common terminal 14 is satisfactorily shorter thanthe spin relaxation length λn of the nonmagnetic base electrode 10,constant and great spin accumulation occurs between the first junctionface and the second junction face in the nonmagnetic base electrode 10regardless of the location in the nonmagnetic base electrode 10.

In the first embodiment, the electrochemical potential μ↑ of up-spinelectrons and the electrochemical potential μ↓ of down-spin electronscan be separated from each other in a short distance within the magneticmaterial by utilizing the short spin diffusion length in the magneticmaterial. Accordingly, it is not necessary to keep the spin relaxationlength λn that is required when an external lead terminal is directlyconnected to a nonmagnetic base electrode in conventional devices.Therefore, the nonmagnetic base electrode 10 can be shortened.

FIG. 12 shows electrochemical potential distributions along the centerline of the nonmagnetic base electrode 10. In the first embodiment, thelength of the nonmagnetic base electrode 10 can be considerably shorterthan the spin relaxation length λn. Accordingly, the spin accumulationdoes not have a large distribution over the entire nonmagnetic baseelectrode 10, but becomes constant and large.

The spin detection terminal 16 is electrically in contact with thenonmagnetic base layer 10. In general, the spin relaxation length λf ina magnetic material is very short, a few nm to a few tens nm.Accordingly, up-spin electrons and down-spin electrons areshort-circuited in a magnetic material. Therefore, if theelectrochemical potentials in the nonmagnetic base electrode 10 havedistributions shown in FIG. 12, down-spin electrons flow into the spindetection terminal 16, and up-spin electrons flow out of the spindetection terminal 16. At this time, since the value of the majoritycarrier specific resistance ρ⁺ of the spin detection terminal 16 differsfrom that of the minority carrier specific resistance ρ⁻, the voltage towhich the electrochemical potential is relaxed in the spin detectionterminal 16 differs between the case where the magnetization of the spininjection terminal 12 and that of the spin detection terminal 16 areparallel to each other and the case where the magnetizations areantiparallel to each other.

FIGS. 13A and 13B show examples of electrochemical potentialdistributions along the path from the common terminal 14 through thenonmagnetic base electrode 10 to the spin detection terminal 16 in thecases where the two magnetizations are antiparallel to each other andparallel to each other. In the case where the magnetizations areparallel to each other, the electrochemical potentials are relaxed to ahigher voltage level, and in the case where they are antiparallel toeach other, the electrochemical potentials are relaxed to a lowervoltage level. Therefore, whether the two magnetizations are parallel orantiparallel to each other can be measured by measuring the voltagelevel.

If the magnetization of the magnetic layer in the spin injectionterminal 12 has an angle θ with the magnetization of the magnetic layerin the spin detection terminal 16, the potential difference meets theequation V=(Vp+Vap)/2−Vs/2·cos θ where Vp is the potential difference inthe case where the magnetizations are parallel to each other, Vap is apotential difference in the case where the magnetizations areantiparallel to each other, and Vs is a difference therebetween(Vap−Vp=Vs). Accordingly, a relative angle between the magnetization ofthe magnetic layer in the spin injection terminal 12 and themagnetization of the magnetic layer in the spin detection terminal 16can be measured by measuring the potential difference. Therefore, thethree-terminal spin valve element 1 according to the first embodimentcan be used as a magnetic sensor of a hard disk head or the like.

Since a longer spin relaxation length λn can make a greater spinaccumulation to have a greater output, a material having a longer spinrelaxation length, such as Cu, Ag, Au, AI, or Mg is preferably used toform the nonmagnetic base electrode 10.

The materials to form the magnetic layers of the spin injection terminal12, the common terminal 14, and the spin detection terminal 16preferably have a great difference between the majority carrier specificresistance ρ⁺ and the minority carrier specific resistance ρ⁻, such asCoFe and CoFeB. More preferably, a half metal, which includes majoritycarriers but substantially no minority carriers, is preferably used. AHeusler alloy-based Co₂Fe(Ge_(0.5)Ga_(0.5)), Co₂Mn(Ge_(0.5)Ga_(0.5)), orCoFeMnSi can be used as the half metal, but any other half metal canalso be used.

The magnetization of the magnetic layer in each of the spin injectionterminal 12 and the common terminal 14 can be pinned by stacking anantiferromagnetic layer so as to be in contact with the magnetic layerto apply a one-directional anisotropy thereto. PtMn or IrMn may be usedto form the antiferromagnetic layer. The magnetic layer, in which themagnetization is to be pinned, may have a so-called synthetic structurein which a material is interposed between upper and lower magneticlayers for helping antiferromagnetic coupling of the magnetic materialsof the upper and lower magnetic layers, as in the structureCoFe/Ru/CoFe. Such a synthetic structure enables a strong magnetizationpinning.

FIG. 14 shows the shapes of the nonmagnetic base layer 10, the magneticlayers of the spin injection terminal 12, the common terminal 14, andthe spin detection terminal 16 when the three-terminal spin valveelement 1 shown in FIG. 10 is viewed from a plane perpendicular to theABS and the moving direction of the magnetic recording medium, i.e., theplane “CT (Cross Track) direction×SH direction.” As shown in FIG. 14, astructure in which the junction areas of the spin injection terminal 12and the common terminal 14 is increased in the CT direction can beobtained by arranging the spin injection terminal 12 and the commonterminal 14 in parallel in the SH direction, and increasing the lengthof the spin injection terminal 12 and the common terminal 14 in the CTdirection, so that the junction areas of the spin injection terminal 12and the common terminal 14 become greater than that of the spindetection terminal 16.

The spin injection terminal 12 and the common terminal 14 may bearranged in the CT direction, and the length in the SH direction thereofmay be made greater to increase the junctions areas of the spininjection terminal 12 and the common terminal 14 as compared to thejunction area of the spin detection terminal 16, as shown in FIG. 15.

FIG. 16 shows the three-terminal spin valve element 1 illustrated inFIG. 10, viewed from the ABS. The three-terminal spin valve element 1 isdisposed between shields 22, 24. A base layer 362, a cap layer 364, andthe spin detection terminal 16 serving as the free layer, and thenonmagnetic base layer 10 are disposed between the shields 22, 24. Thespin injection terminal 12 serving as a pinned layer and the commonterminal 14 are not present on the ABS side. Therefore, the gap betweenthe shields may be narrowed. This is suitable for high-resolutionreproduction of data.

The base layer 362 includes an electrically insulating layer of an oxidelayer (for example MgO), in order to prevent the current leakage betweenthe lower shield 22 and other elements. A IrMn layer 375 is deposited onthe top face of the upper shield 24. The magnetization direction of thefree layer 16 is fixed in the CT direction due to the presence of theIrMn layer 375 and the arrangement of magnetization biasing layers 370a, 370 b on the CT direction sides of the free layer 16. As a result,noise signals from adjacent tracks can be rejected, and themagnetization direction of the free layer 16 can be stably oriented inthe CT direction. The stable magnetization in the CT direction of thefree layer 16 results in good linear response voltage variations causedby the magnetic field of the magnetic recording medium. Therefore, datacan be reproduced with a high signal-to-noise ratio.

The magnetic head including the three-terminal spin valve element 1 hasthree conductor lines connecting to a preamplifier through a suspension.The three conductor lines are not grounded but connected to thepreamplifier 300. Since they are not grounded, differential detectionfor removing disturbance noise can be performed by the preamplifier 300.

In the elements in the first embodiment and other embodiments andexamples described later, a sub current is diverted from the maincurrent flowing between the terminal 12 and the terminal 14 and causedto flow through the resistance 31 of preamplifier 300 for detecting thevoltage, unlike conventional spin accumulation elements. The sub currentis lower than the main current. The current diversion ratio may beadjusted by the values of the line resistance of the common terminal 14and the resistance 31 of the voltage detection line. Specifically, thecurrent diversion ratio may be adjusted by the ratio between the arealresistance RA at the interface of the terminal 14 and the arealresistance RA at the interface of the terminal 16, or the ratio betweenthe junction area of the terminal 14 and the junction area of theterminal 16. Since it is difficult to change the areal resistances RA ofthe three elements, it is easier to adjust the areas.

FIG. 17 shows a result of a simulation for obtaining the relationshipbetween the ratio of the junction area of the terminal 14 to thejunction area of the terminal 16 and the normalized output. The valuesof the normalized output are actual outputs normalized by setting theoutput (ideal output) of an ideal spin accumulation element without adiverted electrical current as 1. The junction area of the terminal 12with the nonmagnetic base layer 10 is set to be the same as that of theterminal 14 with the nonmagnetic base layer 10. The areal resistance RAis the same for all the elements, 0.1 Ωμm². The area of the terminal 16is fixed, 25×25 nm², and the junction areas of the terminals 14, 12 areincreased. It can be found that if the junction area of the terminal 14is more than four times that of the terminal 16, i.e., if the divertedcurrent to the terminal 16 is less than 25% of the main current, theoutput can be maintained to be about 90% of the ideal output. In thecalculation conditions of this case, the current is substantially in therange of the preamplifier current used in currently available HDDs, forexample 0.1 mA to 0.3 mA.

It is preferable that interface layers 352, 354, 356 of a highresistance material such as MgO (with a thickness of about 1 nm), Al—O,or SiO be disposed between each of the terminals 12, 14, 16 and thenonmagnetic base electrode 10.

FIG. 18 shows the relationship between the areal resistance RA of thehigh-resistance interface layer 356 of the free layer 16 and the CTwidth of the free layer 16, and the areal resistance RA of the junctioninterface of the free layer 16. The target CT width of the firstembodiment is 30 nm or less, which is the value difficult to be achievedin currently-available magnetic heads. If the areal resistance RA is toolow, for example less than 0.01 Ωμm² like that of a metal-basedmaterial, the line resistance (for example, 25 to 50Ω) of the conductorconnecting to the preamplifier serves as the main resistance. This makesit difficult to reduce the current diversion ratio on the free layer 16side.

If the areal resistance RA of the free layer 16 exceeds 500 Ωμm², theelectric noise increases to make it difficult to have a highsignal-to-noise ratio. An interface layer having a high areal resistanceRA ranging from 0.025 to 0.3 Ωμm² is preferably selected to achieve asuitable interface resistance (for example, 50 to 500Ω) for the freelayer 16. The hatched portions in FIG. 18 show values inappropriate forthe magnetic heads.

(Manufacturing Method)

A manufacturing method relating to the nonmagnetic base layer 10, thespin injection terminal 12, the common terminal 14, and the spindetection terminal 16 according to the first embodiment will bedescribed below with reference to FIGS. 19 A to 19D.

The nonmagnetic base layer 10, an interface layer 350, and a magneticlayer 380 are sequentially formed in a vacuum deposition apparatus (FIG.19 A). As a result, good crystallinity can be easily obtained around theinterfaces.

Subsequently, the planar shape of the nonmagnetic base layer 10 isdefined by an ordinary patterning step. The magnetic layer 380 on thenonmagnetic base layer 10 is also patterned to have the same shape (FIG.19 B).

Thereafter, the magnetic layer 380 is patterned to form the threemagnetic terminals, the spin injection terminal 12, the common terminal14, and the spin detection terminal 16 (FIG. 19 C). The interface layer350 serves as an etching stopper at this time. As a result, thestructure shown in FIG. 19 D can be obtained.

This manufacturing method provides good crystallinity and avoids theproblem of adjustment in positions of the magnetic terminals 12, 14, and16. Accordingly, magnetic terminals with fine intervals can be obtained.Narrowing the intervals among magnetic terminals allows the control ofthe loss in polarized spin diffusion in the intermediate layer 34.Accordingly, the output can be increased.

The spin injection terminal 12, the common terminal 14, and the spindetection terminal 16 of the spin valve element 1 shown in FIG. 10 arelocated so as to be separated from each other on the same side of thenonmagnetic base electrode 10 along the direction in which thenonmagnetic base electrode 10 extends. However, the spin injectionterminal 12 may be located on the opposite side to the common terminal14 relative to the nonmagnetic base electrode 10 as shown in FIG. 20.Since the current path in the nonmagnetic base electrode 10 in thestructure shown in FIG. 20 is thick, the resistance of the nonmagneticbase electrode 10 can be reduced to a negligible level, and the heatdissipation from the nonmagnetic base electrode 10 becomes good. This isa suitable structure for a large current. Although no interface layerwith a high resistance is disposed between each of the spin injectionterminal 12, the common terminal 14, and the spin detection terminal 16and the nonmagnetic base electrode 10 in the modification shown in FIG.20, the interface layers 352, 354, 356 are preferably disposed in thesame manner as those in the first embodiment shown in FIG. 10.

Furthermore, as will be described later, the spin detection terminal 16of the spin valve element 1 shown in FIG. 10 may be located on theopposite side of the nonmagnetic base electrode 10 to the spin injectionterminal 12 and the common terminal 14.

As described above, according to the first embodiment, a magnetic headincluding a three-terminal spin valve element can be obtained, which maybe used in a hard disk head for reading data from a hard disk devicewith minute recording bits, easy to be downsized, and hard to beaffected by external environment.

This magnetic head has advantages in that a reproducing operation can beperformed without considerably changing the currently-used preamplifiersystems, that downsizing thereof is possible, and that it is unlikely tobe affected by external noise due to its differential detectionoperations.

Second Embodiment

FIG. 21 shows a hard disk head according to the second embodiment. Thehard disk head according to the second embodiment uses the spin valveelement 1 according to the first embodiment as a magnetic sensor. Thehard disk head according to the second embodiment includes the spinvalve element 1 according to the first embodiment, a lower magneticshield 22, and an upper magnetic shield 24. The spin valve element 1includes a nonmagnetic base electrode 10, and a spin injection terminal12, a common terminal 14, and a spin detection terminal 16, which aredisposed on the nonmagnetic base electrode 10 so as to be separated fromeach other. In the second embodiment, the spin injection terminal 12 andthe common terminal 14 are disposed on the same side of the nonmagneticbase electrode 10, and the spin detection terminal 16 is disposed nearone of the terminals of the nonmagnetic base electrode 10 on an oppositeside of the nonmagnetic base electrode 10 to the spin injection terminal12 and the common terminal 14. Although no interface layer with a highresistance is disposed between each of the spin injection terminal 12,the common terminal 14, and the spin detection terminal 16 and thenonmagnetic base electrode 10 in the second embodiment shown in FIG. 21,the interface layers 352, 354, 356 are preferably disposed in the samemanner as those in the first embodiment shown in FIG. 10.

The spin injection terminal 12 includes a magnetization pinned layer 12a and an antiferromagnetic layer 12 b disposed on the magnetizationpinned layer 12 a to pin the magnetization direction of themagnetization pinned layer 12 a. A lead terminal 17 a is disposed on theantiferromagnetic layer 12 b.

The common terminal 14 includes a magnetization pinned layer 14 a and anantiferromagnetic layer 14 b disposed on the magnetization pinned layer14 a to pin the magnetization direction of the magnetization pinnedlayer 14 a. A lead terminal 17 b is disposed on the antiferromagneticlayer 14 b.

A lead terminal 17 c is disposed under the spin detection terminal 16,the lead terminal 17 c connecting to the lower magnetic shield 22. Aninsulating layer 19 for forming a gap is disposed on a region of thenonmagnetic base electrode 10 immediately above the spin detectionterminal 16, so that the nonmagnetic base electrode 10 and the magneticshield 24 are electrically insulated from each other in this region. Thelead terminal 17 b is connected to the upper magnetic shield 24. Thelower magnetic shield 22 includes a first portion connecting to the leadterminal 17 c, and a second portion connecting to the first portion andextending in the direction along the nonmagnetic base electrode 10. Theupper magnetic shield 24 includes a first portion connecting to the leadterminal 17 b on the common terminal 14, a second portion connecting tothe first portion and extending along the ABS, and a third portionconnecting to the first portion and located above an external leadterminal 18. Although no interface layer with a high resistance isdisposed between each of the spin injection terminal 12, the commonterminal 14, and the spin detection terminal 16 and the nonmagnetic baseelectrode 10 in the second embodiment shown in FIG. 21, the interfacelayers 352, 354, 356 are preferably disposed in the same manner as thosein the first embodiment shown in FIG. 10.

The end face of the nonmagnetic base electrode 10 where the spindetection terminal 16 is disposed, the side face of the spin detectionterminal 16 opposite to the common terminal 14, and the side faces ofthe lower magnetic shield 22 and the upper magnetic shield 24 oppositeto the common terminal 14 are on the same plane, which is the ABS.

The lead terminal 18 is connected to an external lead terminal P1, theupper magnetic shield 24 is connected to an external lead terminal P2,and the lower magnetic shield 22 is connected to an external leadterminal P3 of the slider, respectively. The external lead terminal P2and the external lead terminal P1 are connected to the current source 30of the preamplifier 300, and the external lead terminal P3 and theexternal lead terminal P2 are connected to the resistance 31 of thepreamplifier 300. This causes a sense current to flow between the spininjection terminal 12 and the common terminal 14, and the voltagebetween the common terminal 14 and the spin detection terminal 16 viathe nonmagnetic base electrode 10 is measured by a voltmeter 32.

An insulating layer 25 of, for example, alumina, is formed between thespin valve element 1 and the lower magnetic shield 22 and between thespin valve element 1 and the upper magnetic shield 24 to preventunnecessary electric contact.

(Modification)

FIG. 22 shows a hard disk head according to a modification of the secondembodiment. The hard disk head according to the modification is obtainedby replacing the positions of the spin injection terminal 12 and thespin detection terminal 16, and using the magnetic layers 16 a, 14 a ofthe spin detection terminal 16 and the common terminal 14 asmagnetization pinned layers and the magnetic layer of the spin injectionterminal 12 as a free layer in the hard disk head shown in FIG. 21. Inthis case, the magnetization directions of the magnetic layers 16 a, 14a in the spin detection terminal 16 and the common terminal 14 arepinned to be parallel to each other. The current source 30 of thepreamplifier 300 is connected to an external lead terminal P3 of thelower magnetic shield 22 and an external lead terminal P2 of the uppermagnetic shield 24, and the resistance 31 of the preamplifier 300 isconnected to an external lead terminal P1 and the external lead terminalP2. Although no interface layer with a high resistance is disposedbetween each of the spin injection terminal 12, the common terminal 14,and the spin detection terminal 16 and the nonmagnetic base electrode 10in the modification shown in FIG. 22, the interface layers 352, 354, 356are preferably disposed in the same manner as those in the firstembodiment shown in FIG. 10.

In the modification, the angle formed by the magnetization of themagnetization pinned layers 16 a, 14 a of the spin detection terminal 16and the common terminal 14 and the magnetization of the magnetic layerof the spin injection terminal 12 serving as a free layer varies inaccordance with an external magnetic field. As the angle becomes closerto the antiparallel direction, the spin accumulation of the nonmagneticbase electrode 10 increases, and as it becomes closer to the paralleldirection, the spin accumulation decreases. Therefore, the voltage ofthe spin detection terminal 16 varies. The degree of the externalmagnetic field can be detected using this feature. In the arrangementshown in FIG. 22, the magnetizations of the magnetization pinned layers16 a, 14 a in the spin detection terminal 16 and the common terminal 14are not needed to be antiparallel to each other. Accordingly, themagnetic head can be manufactured more easily.

Example 1

FIG. 23 shows a hard disk head according to Example 1. The hard diskhead according to Example 1 is the hard disk head according to thesecond embodiment, which is manufactured in the following manner.

First, a layer of Co₂Fe(Ge_(0.5)Ga_(0.5)) Heusler alloy (herein afterreferred to “CFGG”), which is a half metal, is formed as the spindetection terminal 16 by a sputtering method on the lower magneticshield 22 with the lead terminal 17 c of Cu having a thickness of 2 nmdisposed therebetween. The dimensions of the spin detection terminal 16are 5 nm in thickness, 12 nm in width (extending in the directionparallel to the ABS), and 10 nm in length (extending in the directionperpendicular to the ABS). A gap film 25 of alumina is formed tosurround the spin detection terminal 16. The nonmagnetic base electrode10 formed on the gap film 25 and the lower magnetic shield 22 arearranged so as not to be in contact with each other unnecessarily. Then,a layer of Cu to serve as the nonmagnetic base electrode 10 is formed tooverlap the spin detection terminal 16 by a sputtering method in twosteps to have a length of 100 nm, a width of 12 nm, and a thickness of10 nm from the junction face with the spin injection terminal 12 to thejunction face with the common terminal 14, and the same length and widthand a thickness of 5 nm from the junction face with the common terminal14 to the junction face with the spin detection terminal 16.

Subsequently, the spin injection terminal 12 and the common terminal 14are formed by a sputtering method on the nonmagnetic base electrode 10.The magnetization pinned layer 12 a of the spin injection terminal 12has a synthetic structure including a spacer of Ru. Specifically, thespin injection terminal 12 has a multilayer structure in which a CFGGlayer 12 a ₁ having a thickness of 5 nm, a CoFe layer 12 a ₂ having athickness of 1 nm, a Ru layer 12 a ₃ having a thickness of 1 nm, a CoFelayer 12 a ₄ having a thickness of 4 nm, and an antiferromagnetic layer12 b of IrMn having a thickness of 10 nm are stacked in this order. As aresult, the magnetic layer 12 a ₄ on the IrMn layer side has a greatermagnetization in the spin injection terminal 12.

The magnetization pinned layer 14 a of the common terminal 14 also has asynthetic structure including a spacer of Ru. Specifically, the commonterminal 14 has a multilayer structure in which a CFGG layer 14 a ₁having a thickness of 5 nm, a CoFe layer 14 a ₂ having a thickness of 1nm, a Ru layer 14 a ₃ having a thickness of 1 nm, a CoFe layer 14 a ₄having a thickness of 3 nm, and an antiferromagnetic layer 14 b of IrMnhaving a thickness of 10 nm are stacked in this order. As a result, themagnetic layer 14 a ₁ on the CFGG layer side has a greater magnetizationin the common terminal 14.

Thus, the thicknesses of the synthetic structures are different fromeach other. As a result, when the magnetization of the magnetizationpinned layers are pinned by magnetic field annealing during which amagnetic field is applied to the spin valve element in the longitudinaldirection (the direction in which the nonmagnetic base electrode 10extends), the magnetization of the magnetic layer 12 ₄ on the IrMn layerside, which is greater, in the spin injection terminal 12 is orientedtoward the direction of magnetic field, and hence the magnetization ofthe magnetic layer 12 a ₂ on the nonmagnetic base electrode 10 side isoriented to be antiparallel to the magnetic field. In contrast, themagnetization of the magnetic layer 14 ₂ on the CFGG layer side, whichis greater, in the common terminal 14 is oriented toward the magneticfield and hence pinned in the direction parallel to the magnetic field.In this manner, the magnetization directions of the magnetic layers 12 a₂, 14 a ₂ of the spin injection terminal 12 and the common terminal 14can be pinned to be antiparallel to each other. Both the spin injectionterminal 12 and the common terminal 14 have a width of 12 nm and alength of 10 nm. The spin injection terminal 12 and the common terminal14 are covered by an alumina gap film except for through-holes on thetop faces thereof so as to be insulated from the upper magnetic shield24. The top face of the spin injection terminal 12 is connected via thelead terminal 17 a of Cu to the external lead terminal 18 of Cu thatfurther connects to the current source 30, and the common terminal 14 isconnected via the lead terminal 17 b of Cu to the upper magnetic shield24. Although no interface layer with a high resistance is disposedbetween each of the spin injection terminal 12, the common terminal 14,and the spin detection terminal 16 and the nonmagnetic base electrode 10in Example 1 shown in FIG. 23, the interface layers 352, 354, 356 arepreferably disposed in the same manner as those in the first embodimentshown in FIG. 10.

In Example 1, the external lead terminal P1 connecting to the externallead terminal 18 and the external lead terminal P2 of the upper magneticshield 24 in the slider are connected to the current source 30 of thepreamplifier 300, and the external lead terminal P2 of the uppermagnetic shield 24 and the external lead terminal P3 of the lowermagnetic shield 22 are connected to the resistance 31 of thepreamplifier 300.

With such a structure, a gap of 15 nm can be obtained between the lowermagnetic shield 22 and the upper magnetic shield 24, and a head outputof 2 mV can be obtained from a sense current of 50 μA. As a result, ahead SN ratio of 25 dB can be obtained by using Example 1 in combinationwith a magnetic medium of 5 Tbit/in².

Example 2

FIG. 24 shows a hard disk head according to Example 2. The hard diskhead according to Example 2 is the hard disk head according to thesecond embodiment, and having the same structure as the hard disk headaccording to Example 1, except that the materials of the spin injectionterminal 12, the common terminal 14, and the spin detection terminal 16are different. The dimensions of the respective elements are the same asthose of Example 1. The spin detection terminal 16 of Example 2 has amultilayer structure including a CoFeB layer 16 ₁ having a thickness of5 nm, and an interface layer 16 ₂ of MgO having a thickness of 1 nmformed on the CoFeB layer 16 ₁.

The spin injection terminal 12 is formed on an interface layer 13 a ofMgO having a thickness of 1 nm, which is disposed on the nonmagneticbase electrode 10, and includes a magnetic layer 12 a and anantiferromagnetic layer 12 b of PtMn having a thickness of 10 nm, whichis disposed on the magnetic layer 12 a and pins the magnetizationdirection of the magnetic layer 12 a. The magnetic layer 12 a has asynthetic structure including a spacer of Ru. Specifically, the magneticlayer 12 a has a multilayer structure in which a CoFeB layer 12 a ₂having a thickness of 4 nm, a Ru layer 12 a ₃ having a thickness of 1nm, and a CoFeB layer 12 a ₄ having a thickness of 5 nm are stacked inthis order.

The common terminal 14 is formed on an interface layer 13 b of MgOhaving a thickness of 1 nm disposed on the nonmagnetic base electrode10, and includes a magnetic layer 14 a and an antiferromagnetic layer 14b of PtMn having a thickness of 10 nm, disposed on the magnetic layer 14a to pin the magnetization direction of the magnetic layer 14 a. Themagnetic layer 14 a has a synthetic structure including a spacer of Ru.Specifically, the magnetic layer 14 a has a multilayer structure inwhich a CoFeB layer 14 a ₂ having a thickness of 5 nm, a Ru layer 14 a ₃having a thickness of 1 nm, and a CoFeB layer 14 a ₄ having a thicknessof 4 nm are stacked in this order.

In Example 2, the external lead terminal P1 connecting to the leadterminal 18 and the external lead terminal P2 of the upper magneticshield 24 in the slider are connected to the current source 30 of thepreamplifier 300, and the external lead terminal P2 of the uppermagnetic shield 24 and the external lead terminal P3 of the lowermagnetic shield 22 are connected to the resistance 31 of thepreamplifier 300.

When the spin injection and the spin detection are performed through atunnel junction of CoFeB and MgO as in the above structure, theresistance value between terminals on the spin detection side becomes ashigh as 3 kΩ. However, an output as large as 5 mV can be obtained with asense current of 30 μA. Therefore, if the hard disk head according toExample 2 is combined with a magnetic recording medium of 5 Tbit/in², ahead output of 25 dB can be obtained.

Example 3

FIG. 25 shows a hard disk head according to Example 3. The hard diskhead of Example 3 is the hard disk head according to a modification ofthe second embodiment shown in FIG. 22, and the dimensions of therespective elements are the same as those of Example 1. Thus, themagnetic layers of the common terminal 14 and the spin detectionterminal 16 are magnetization pinned layers.

The common terminal 14 has a multilayer structure in which a CFGG layer14 a ₁ having a thickness of 5 nm, a CoFeB layer 14 a ₂ having athickness of 1 nm, a Ru layer 14 a ₃ having a thickness of 1 nm, a CoFeBlayer 14 a ₄ having a thickness of 4 nm, and a PtMn layer 14 b having athickness of 10 nm are stacked in this order. Thus, the magnetic layer14 a has a synthetic structure including the CFGG layer 14 a ₁, theCoFeB layer 14 a ₂, the Ru layer 14 a ₃, and the CoFeB layer 14 a ₄.

Similarly, the spin detection terminal 16 has a multilayer structure inwhich a CFGG layer 16 a ₁ having a thickness of 5 nm, a CoFeB layer 16 a₂ having a thickness of 1 nm, a Ru layer 16 a ₃ having a thickness of 1nm, a CoFeB layer 16 a ₄ having a thickness of 4 nm, and a PtMn layer 16b having a thickness of 10 nm are stacked in this order. Thus, themagnetic layer 16 a has a synthetic structure including the CFGG layer16 a ₁, the CoFeB layer 16 a ₂, the Ru layer 16 a ₃, and the CoFeB layer16 a ₄.

The spin injection terminal 12 includes a CFGG layer having a thicknessof 5 nm. Although no interface layer with a high resistance is disposedbetween each of the spin injection terminal 12, the common terminal 14,and the spin detection terminal 16 and the nonmagnetic base electrode 10in Example 3 shown in FIG. 25, the interface layers 352, 354, 356 arepreferably disposed in the same manner as those in the first embodimentshown in FIG. 10.

In Example 3, the external lead terminal P3 of the lower magnetic shield22 and the external lead terminal P2 of the upper magnetic shield 24 areconnected to the current source 30 of the preamplifier 300, and theexternal lead terminal P1 connecting to the lead terminal 18 and theexternal lead terminal P2 of the upper magnetic shield 24 are connectedto the resistance 31 of the preamplifier 300.

The two terminals, the common terminal 14 and the spin detectionterminal 16, of Example 3 have the same structure. Accordingly, themagnetizations thereof are pinned to the same direction if magneticfield annealing is performed thereon with a magnetic field being appliedin the longitudinal direction of the spin valve element. In contrast, amagnetic field bias is applied to the spin injection terminal 12 havinga magnetic layer serving as a free layer by means of a hard bias filmdisposed on the side face of the spin injection terminal 12.Accordingly, the magnetization thereof is in parallel to the ABS. If arecording magnetic field is applied from a recording medium in thisstate, the magnetization of the magnetic layer, which is a free layer,of the spin injection terminal 12 is rotated. In accordance with therotation, the amount of spin accumulation in the nonmagnetic baseelectrode 10 of Cu varies. Specifically, as the magnetization directionsof the magnetic layers in the spin injection terminal 12 and the commonterminal 14 become close to the antiparallel directions, the spinaccumulation increases, and as they become close to the paralleldirections, the spin accumulation decreases. As a result, the voltagegenerated at the spin detection terminal 16 including the magnetizationpinned layer varies. An output can be obtained by detecting such avoltage. An output of 1.5 mV can be obtained using a sense current of 50μA.

Example 4

FIG. 26 shows a hard disk head according to Example 4. In the hard diskhead according to Example 4, the spin injection terminal 12 is disposedbetween the lower magnetic shield 22 and the nonmagnetic base electrode10 of Cu, and connected to the lower magnetic shield 22 via the leadterminal 17 a of Cu. The spin injection terminal 12 has, on the leadterminal 17 a, a multilayer structure in which an antiferromagneticlayer 12 b of PtMn having a thickness of 10 nm, a CoFeB layer 12 a ₄having a thickness of 4 nm, a Ru layer 12 a ₃ having a thickness of 1nm, a CoFeB layer 12 a ₂ having a thickness of 1 nm, and a CFGG layer 12a ₁ having a thickness of 5 nm are stacked in this order. The CoFeBlayer 12 a ₄, the Ru layer 12 a ₃, the CoFeB layer 12 a ₂, and the CFGGlayer 12 a ₁ form a magnetic layer 12 a having a synthetic structure.The CFGG layer 12 a ₁ is connected to the lower face of the nonmagneticbase electrode 10. The spin injection terminal 12 has a width of 12 nmand a length of 10 nm. The nonmagnetic base electrode 10 of Cu has alength of nm, a width of 12 nm, and a thickness of 10 nm. Incidentally,the length means the dimension in the direction along which thenonmagnetic base electrode 10 extends. The thickness means the dimensionbetween the top face and the bottom face, and the width means thedimension in the direction perpendicular to the length direction and thethickness direction.

The common terminal 14 is disposed on a face of the nonmagnetic baseelectrode 10 opposite to a face where the spin injection terminal 12 isdisposed, so as to be substantially opposed to the spin injectionterminal 12. The common terminal 14 has a multilayer structure in whicha CFGG layer 14 a ₁ having a thickness of 3 nm, a CoFeB layer 14 a ₂having a thickness of 1 nm, a Ru layer 14 a ₃ having a thickness of 1nm, a CoFeB layer 14 a ₄ having a thickness of 5 nm, and anantiferromagnetic layer 14 b of PtMn having a thickness of 10 nm arestacked in this order. The CFGG layer 14 a ₁, the CoFeB layer 14 a ₂,the Ru layer 14 a ₃, and the CoFeB layer 14 a ₄ form a magnetic layer 14a having a synthetic structure. The common terminal 14 is connected tothe lead terminal 18 via a lead terminal 17 b on the antiferromagneticlayer 14 b.

The spin detection terminal 16 is disposed on the same side as thecommon terminal 14 on the nonmagnetic base electrode 10, and includes aCFGG layer having a thickness of 5 nm. A lead terminal 17 c of Cu havinga thickness of 2 nm is formed on the CFGG layer 16. The spin detectionterminal 16 is connected to the upper magnetic shield 24 via the leadterminal 17 c. The spin detection terminal 16 and the lead terminal 17 cproject from an end face of the nonmagnetic base electrode 10 toward theABS. The spin detection terminal 16 has a width of 12 nm, a length of 10nm, and a thickness of 5 nm.

An insulating layer 25 is formed between the nonmagnetic base electrode10 and the lower magnetic shield 22, and between the nonmagnetic baseelectrode 10 and the upper magnetic shield 24 so that they are notdirectly in contact with each other. The insulating layer 25 is formedof, for example, alumina. Although no interface layer with a highresistance is disposed between each of the spin injection terminal 12,the common terminal 14, and the spin detection terminal 16 and thenonmagnetic base electrode 10 in Example 4 shown in FIG. 26, theinterface layers 352, 354, 356 are preferably disposed in the samemanner as those in the first embodiment shown in FIG. 10.

Hard magnetic films (not shown) are disposed on both sides of the spindetection terminal 16 to apply a bias magnetic field thereto, so thatthe magnetization of the spin detection terminal 16 is oriented to thedirection parallel to the ABS. An annealing in the magnetic field isperformed so that the magnetization directions of the CFGG layers 12 a₁, 14 a ₁ of the spin injection terminal 12 and the common terminal 14are pinned to be antiparallel to each other.

In Example 4, the external lead terminal P1 of the lower magnetic shield22 and the external lead terminal P2 connecting to the lead terminal 18are connected to the current source 30 of the preamplifier 300, and theexternal lead terminal P2 and the external lead terminal P3 of the uppermagnetic shield 24 are connected to the resistance 31 of thepreamplifier 300.

With such a structure, a gap of 15 nm can be obtained between themagnetic shields, and a head output of 2 mV can be obtained from a sensecurrent of 50 μA as in the case of Example 1. As a result, a head SN of25 dB can be obtained when the magnetic head of Example 4 is used incombination with a magnetic recording medium of 5 Tbit/in².

Example 5

The hard disk head according to Example 1 shown in FIG. 23 is modifiedso that the spin injection terminal 12 has a simple magnetizationpinning structure instead of the synthetic structure. Specifically, thespin injection terminal shown in FIG. 23 is modified to have amultilayer structure in which a CFGG layer having a thickness of 5 nm, aCoFeB layer having a thickness of 1 nm, and an antiferromagnetic layerof IrMn having a thickness of 10 nm are stacked in this order. Exceptfor this, Example 5 has the same structure as Example 1.

In Example 5, the spin injection terminal does not have a syntheticstructure, but the common terminal has a synthetic structure.Accordingly, if magnetization-pinning annealing is performed under ahigh magnetic field by which the magnetizations of the syntheticstructure are oriented to the same direction, the magnetization of thespin injection terminal and the magnetization of the CFGG layer of thecommon terminal are pinned to be antiparallel to each other under a lowmagnetic field immediately after the magnetizing.

With such a structure, a gap of 15 nm can be obtained between the lowermagnetic shield and the upper magnetic shield, and a head output of 2 mVcan be obtained from a sense current of 50 μA. As a result, a head SN of25 dB can be obtained if the hard disk head of Example 5 is combinedwith a magnetic recording medium having a 5 Tbit/in².

Comparative Example 1

FIG. 27 shows a hard disk head according to Comparative Example 1, whichcorresponds to Example 1. The hard disk head according to ComparativeExample 1 is obtained by replacing the spin injection terminal 12 with aCu layer 13 in the hard disk head according to Example 1 shown in FIG.23. Except for the Cu layer 13, Comparative Example 1 has the samestructure as Example 1.

In Comparative Example 1, the spin accumulation in the nonmagnetic baseelectrode 10 is considerably decreased by the lead terminal 18, and onlyan output of 0.2 mV can be obtained from a sense current of 50 μA.Therefore, no output can be read if Comparative Example 1 is combinedwith a magnetic recording medium of 5 Tbit/in².

Comparative Example 2

FIG. 28 shows a hard disk head according to Comparative Example 2. Thehard disk head according to Comparative Example 2 is obtained byincreasing the length of the nonmagnetic base electrode 10 of Cu so thatthe distance between the Cu layer 13 and the common terminal 14 reaches100 nm in the hard disk head of Comparative Example 1.

Since the spin relaxation length in Cu is about 400 nm in ComparativeExample 2, the length of the nonmagnetic base electrode 10 is notsufficient to obtain satisfactory spin accumulation. In addition, sincethe length of the nonmagnetic base electrode 10 is increased, theresistance between the external lead terminal 18 and the spin detectionterminal 16 is increased, which increases thermal noise. Furthermore,the heat generated by the sense current increases, and the thermalstability is degraded. Moreover, the probability of generating defectsin the process increases, and the yield is reduced. Due to the influenceof the foregoing, only an output of 0.5 mV is obtained and only asignal-to-noise ratio of 15 dB is obtained from a sense current of 50μA. Therefore, even if Comparative example 2 is combined with a magneticrecording medium of 5 Tbit/in², no output can be read.

Comparative Example 3

FIG. 29 shows a three-terminal spin valve element according toComparative Example 3. The three-terminal spin valve element ofComparative Example 3 is manufactured in the following manner. A Culayer 23 is formed on a lower magnetic shield 22. The Cu layer 23 issurrounded by an insulating layer of, for example, alumina (not shown).Thereafter, a nonmagnetic base electrode 10 of Cu is formed on theinsulating layer by a sputtering method so as to connect to the Cu layer23. The nonmagnetic base electrode 10 has a thickness of 5 nm, a widthof 12 nm, and a length of 100 nm. A spin injection terminal 12 and aspin detection terminal 16 are formed by a sputtering method so as to bein contact with the nonmagnetic base electrode 10. The spin injectionterminal 12 includes a magnetic layer 12 a having a synthetic structureincluding a spacer of Ru, and an antiferromagnetic layer 12 b formed onthe magnetic layer 12 a. The magnetic layer 12 a has a multilayerstructure, in which a CFGG layer having a thickness of 4 nm, a CoFelayer having a thickness of 1 nm, a Ru layer having a thickness of 1 nm,and a CoFe layer having a thickness of 5 nm are stacked in this order.The antiferromagnetic layer 12 b is formed of PtMn having a thickness of10 nm.

The spin detection terminal 16 is formed by depositing a CFGG Heusleralloy, which is a half metal, by a sputtering method. The spin detectionterminal 16 has a thickness of 5 nm, a width of 12 nm, and a length of10 nm.

A Cu layer having a thickness of 2 nm and an alumina gap filmsurrounding the Cu layer are formed so that the upper portion of thespin injection terminal 12 is connected to an upper magnetic shield 24 avia a through-hole filled with Cu (not shown). Furthermore, a Cu layerhaving a thickness of 2 nm and an alumina gap film surrounding the Culayer are formed so that the upper portion of the spin detectionterminal 16 is connected to an upper magnetic shield 24 b via athrough-hole filled with Cu (not shown). Thereafter, the upper magneticshields 24 a, 24 b are formed.

The magnetization of the magnetic layer in the spin injection terminal12 is pinned by an annealing in a magnetic field, in which the magneticfield is applied in the longitudinal direction of the spin valve element(the direction in which the nonmagnetic base electrode extends). Thespin detection terminal 16 biases the magnetization so as to be parallelto the ABS by means of a hard film formed on the side face thereof.

With such a structure, the gap between the lower magnetic shield 22 andthe upper magnetic shield 24 b can be set at 15 nm.

In Comparative Example 3, the external lead terminal P2 of the lowermagnetic shield 22 and the external lead terminal P1 of the uppermagnetic shield 24 a are connected to the current source 30 of thepreamplifier 300, and the external lead terminal P2 of the lowermagnetic shield 22 and the external lead terminal P3 of the uppermagnetic shield 24 b are connected to the resistance 31 of thepreamplifier 300.

However, since the nonmagnetic base electrode 10 is connected to thelower magnetic shield 22 at a short distance via the through-hole filledwith Cu 23 of a nonmagnetic material, the spin accumulation in thenonmagnetic base electrode 10 is short-circuited by the lower magneticshield 22. As a result, substantially no spin accumulation occurs.Furthermore, the material used to form the magnetic shields does nothave satisfactory spin polarization. As a result, unnecessary spinscattering occurs at a junction face. Moreover, the magnetization of thelower magnetic shield 22 is varied by an external magnetic field, whichleads to noises, and hence a good signal-to-noise ratio cannot beobtained. A magnetic shield is designed to function as a magneticshield, but is not intended to cause a spin valve MR. Accordingly,Comparative Example 3 cannot work as a hard disk head for reproducingsignals from a magnetic recording medium.

Comparative Example 4

FIG. 30 shows a hard disk head according to Comparative Example 4. Thehard disk head according to Comparative Example 4 is obtained byincreasing the length of the nonmagnetic base electrode 10 of Cu to be100 nm in the hard disk head according to Comparative Example 3.

Since the spin relaxation length of Cu is about 400 nm, the length ofthe nonmagnetic base electrode 10 is not satisfactory in ComparativeExample 4. Accordingly the spin accumulation cannot be obtainedsufficiently. In addition, since the length of the nonmagnetic baseelectrode 10 is increased, the resistance between the lower magneticshield 22 and the spin detection terminal increases to increase thethermal noise. Furthermore, the heat generated by a sense currentincreases and the thermal stability degrades. Moreover, the probabilityof generating defects in the process increases, and the yield isreduced. Due to the influences of the foregoing, the hard disk headaccording to Comparative Example 5 cannot reproduce signals from amagnetic recording medium.

As described above, according to the second embodiment and itsmodifications, and respective Examples, magnetic heads capable ofperforming a reproducing operation with a preamplifier system, reducingthe size, and being unlikely to be affected by external factors can beprovided.

Third Embodiment

A magnetic recording and reproducing apparatus according to the thirdembodiment will be described below.

The hard disk head according to the second embodiment described above isincorporated into, for example, a recording and reproducing typemagnetic head assembly, and further incorporated into a magneticrecording and reproducing apparatus (HDD). The magnetic recording andreproducing apparatus according to the third embodiment may have areproducing function, and may have both a recording function and areproducing function.

FIG. 31 is a perspective view showing a structure of the magneticrecording and reproducing apparatus according to the third embodiment.As shown in FIG. 31, the magnetic recording and reproducing apparatusincludes a housing 110. The housing 110 includes a base 112 in arectangular box shape, of which the top face is open, and a top cover114 to be fastened to the base 112 by a plurality of bolts 111 to closethe opening on the top face of the base 112. The base 112 includes abottom plate 112 a in a rectangular shape, and a sidewall 112 b standingalong the periphery of the bottom plate 112 a.

The housing 110 houses a magnetic disk 116 serving as a recordingmedium, and a spindle motor 118 serving as a driving unit for supportingand rotating the magnetic disk 116. The spindle motor 118 is disposed onthe bottom plate 112 a. The housing 110 has a size enabling the housingof plural, for example two, magnetic disks, and the spindle motor 118 iscapable of supporting and driving two magnetic disks.

The housing 110 also houses a plurality of hard disk heads 117 forrecording information to and reproducing information from the magneticdisk 116, a head stack assembly (“HSA”) 122 for supporting the hard diskheads 117 so as to be freely moved relative to the magnetic disk 116, avoice coil motor (“VCM”) 124 for pivoting and positioning the HSA 122, aramp loading mechanism 125 for moving and holding the hard disk head 117at a retracting position that is at a distance from the magnetic disk116 when the hard disk head 117 reaches the outermost portion of themagnetic disk 116, a latch mechanism 126 for holding the HSA 122 at theretreating position when an impact is given to the HDD, and a substrateunit 121 including a preamplifier. A printed circuit board that is notshown is fastened by bolts to the outer surface of the bottom plate 112a of the base 112. The printed circuit board controls operations of thespindle motor 118, the VCM 124, and the hard disk heads 117 via thesubstrate unit 121. A circulation filter 123 for capturing dusts withinthe housing by driving a movable portion thereof is provided to asidewall of the base 112 at a position outside the magnetic disk 116.

The magnetic disk 116 has a diameter of, for example, 65 mm (2.5inches), and includes magnetic recording layers under the top face andabove the bottom face. The magnetic disk 116 is coaxially engaged with ahub (not shown) of the spindle motor 118, and clamped by a clamp spring127 to be fixed to the hub. In this manner, the magnetic disk 116 issupported to be in parallel with the bottom plate 112 a of the base 112.The magnetic disk 116 is rotated by the spindle motor 118 at apredetermined speed, for example, 5400 rpm or 7200 rpm.

FIG. 32 is a perspective view showing the head stack assembly (HSA) 122of the magnetic recording and reproducing apparatus according to thethird embodiment, and FIG. 33 is an exploded perspective view of the HSA122. As shown in FIGS. 32 and 33, the HSA 122 includes a bearing unit128 that can be freely rotated, two head gimbal assemblies (“HGAs”) 130extending from the bearing unit 128, a spacer ring 144 disposed withinthe HGAs 130, and a dummy spacer 150.

The bearing unit 128 is located along the longitudinal direction of thebase 112 at a distance from the rotation center of, and near the outerperiphery of the magnetic disk 116. The bearing unit 128 includes apivot axis 132 standing on the bottom plate 112 a of the base 112, andsleeve 136 in a cylindrical shape, which is coaxially supported by thepivot axis 132 so as to be rotated freely around the pivot axis 132 viathe bearings 134. A flange 137 in a ring shape is disposed on the upperportion of the sleeve 136, and a screw portion 138 is formed on theouter periphery of the lower portion. The sleeve 136 of the bearing unit128 has a size, i.e., a length in the axial direction, sufficientlyenough to fix, for example, at maximum of four HGAs and spacers betweenthe adjacent HGAs 140.

In the third embodiment, the number of magnetic disk 116 is one.Accordingly, two HGAs 130, which are fewer than the maximum attachablenumber of four, are fixed to the bearing unit 128. Each HGA 130 includesan arm 140 extending from the bearing unit 128, a suspension 142extending from the arm, and a hard disk head 117 supported at theextended end of the suspension via a gimbal portion.

The arm 140 has a laminate structure of, for example, stainless steel,aluminum, and stainless steel, and in a thin flat plate shape. Acircular through-hole 141 is formed on one end, i.e., the base endthereof. The suspension 142 is formed of a narrow and long leaf spring,the base portion of which is fixed to an end of the arm 140 by spotwelding or gluing so that the suspension 142 extends from the arm 140.The suspension 142 and the arm 140 may be integrally formed of the samematerial.

The hard disk head 117 is one of the magnetic heads according to thesecond embodiment, and includes a substantially rectangular slider (notshown) and a recording head formed on the slider. The hard disk head 117is fixed to the gimbal portion formed at a tip portion of the suspension142. Furthermore, the hard disk head 117 includes four electrodes, whichare not shown. A relay flexible printed circuit board (“relay FPC”) isdisposed on the arm 140 and the suspension 142, and the hard disk head117 is electrically connected to a main FPC 121 b via the relay FPC.

The spacer ring 144 is formed of aluminum or the like to have apredetermined thickness and a predetermined outside diameter. A supportframe 146 of a synthetic resin is integrally formed with the spacer ring144 and extends outwardly from the spacer ring. A voice coil 147 of theVCM 124 is fixed to the support frame 146.

The dummy spacer 150 includes a spacer body 152 in an annular shape, anda balance adjusting portion 154 extending from the spacer body. Thedummy spacer 150 is integrally formed of a metal such as stainlesssteel. The outside diameter of the spacer body 152 is the same as thatof the spacer ring 144. Therefore, the outside diameter of a portion ofthe spacer body 152 contacting the arm is the same as the outsidediameter of a portion of the spacer ring 144 contacting the arm. Thethickness of the spacer body 152 is the sum of the thicknesses of thearms of the HGAs, the number of which is fewer than the maximum number,two in this case, and the thicknesses of the spacer rings disposedtherebetween.

The dummy spacer 150, the two HGAs 130, and the spacer ring 144 areengaged with the outer periphery of the sleeve 136 of the bearing unit128 with the sleeve 136 being inserted into the inner hole of the spacerbody 152, the through-hole 141 of the arm 140, and the inner hole of thespacer ring. Thus the dummy spacer 150, the two HGAs 130, and the spacerring 144 are stacked on the flange 137 along the axial direction of thesleeve. The spacer body 152 of the dummy spacer 150 is engaged with theouter periphery of the sleeve 136 so as to be disposed between theflange 137 and one of the arms 140, and the spacer ring 144 is engagedwith the outer periphery of the sleeve 136 so as to be disposed betweenthe two arms 140. A washer 156 in an annular shape is engaged with thelower periphery of the sleeve 136.

The dummy spacer 150, the two arms 140, the spacer ring 144, and thewasher 156 engaged with the outer periphery of the sleeve 136 aresandwiched between a nut 158 engaged with the screw portion 138 of thesleeve 136 and the flange 137 to be fixed to the outer periphery of thesleeve.

The two arms 140 are located at predetermined positions in thecircumferential direction of the sleeve 136, and extend in the samedirection from the sleeve. As a result, the two HGAs are integrallyrotated with the sleeve 136, and face each other with a predetermineddistance therebetween in parallel with the surface of the magnetic disk116. The support frame 146 integrally formed with the spacer ring 144extends from the bearing unit 128 in the opposite direction to the arms140. Two terminals 160 in a pin shape project from the support frame146, and electrically connect to the voice coil 147 via a wiring (notshown) embedded in the support frame 146.

The suspension 142 has lead lines (not shown) for writing and readingsignals, which are electrically connected to respective electrodes ofthe magnetic head incorporated into the slider. Furthermore, anelectrode pad (not shown) is provided to the magnetic head assembly 130.

A signal processing unit (not shown) for writing signals to and readingsignals from the magnetic recording medium using the magnetic head isprovided. The signal processing unit is disposed on the back side of themagnetic recording and reproducing apparatus shown in FIG. 31, forexample. The input and output lines of the signal processing unit areconnected to the electrode pad and electrically coupled to the magnetichead.

Thus, the magnetic recording and reproducing apparatus according to thethird embodiment includes a magnetic recording medium, any of the harddisk heads according to the second embodiment, a movable unit (movementcontroller) for separating the magnetic recording medium and the harddisk head from each other, or moving the magnetic recording medium andthe hard disk head relative to each other under a contact state, aposition controller for positioning the hard disk head at apredetermined recording position of the magnetic recording medium, and asignal processing unit for writing signals to and reading signals fromthe magnetic recording medium using the hard disk head. The recordingmedium disk 116 can be used as the aforementioned magnetic recordingmedium. The aforementioned movable unit may include a slider.Furthermore, the aforementioned position controller may include an HSA122.

When the magnetic disk 116 is rotated, and the actuator arm 140 iscaused to pivot by the voice coil motor 124 to load the slider onto themagnetic disk 116, the air bearing surface (ABS) of the slider on whichthe hard disk head is mounted is held above the surface of the magneticdisk 116 at a predetermined floating distance therefrom. In this manner,the information recorded on the magnetic disk 116 is read based on theaforementioned principle. FIG. 34 shows the ABS of a slider 400. Theexternal lead terminals P1, P2, P3 of the three-terminal spin valveelement 1 in the magnetic head are disposed at the ABS of the slider400. The ABS includes external lead terminals Q1, Q2 of recording, andexternal lead terminals R1, R2 for adjusting the floating amount of theslider.

The magnetic recording and reproducing apparatus according to the thirdembodiment, which uses any of the hard disk heads according to thesecond embodiment, is capable of increasing the output voltage, anddecreasing the gap between shields.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

The invention claimed is:
 1. A magnetic head comprising: a spin valveelement with three terminals including: a nonmagnetic base layer, afirst terminal including a first magnetic layer, in which a direction ofmagnetization is switchable, the first terminal connecting to a portionnear one of opposing end faces of the nonmagnetic base layer in adirection along which the nonmagnetic base layer extends, a secondterminal including a second magnetic layer, in which a direction ofmagnetization is pinned, the second terminal connecting to thenonmagnetic base layer so as to be at a distance from the first terminalalong the direction in which the nonmagnetic base layer extends, and athird terminal including a third magnetic layer, in which a direction ofmagnetization is pinned to be antiparallel to the direction ofmagnetization of the second magnetic layer, the third terminalconnecting to the nonmagnetic base layer so as to be at distances fromthe first terminal and the second terminal along the direction in whichthe nonmagnetic base layer extends; and a slider including a firstexternal lead terminal connecting to the first terminal, a secondexternal lead terminal connecting to the second terminal, and a thirdexternal lead terminal connecting to the third terminal, in anoperation, a first current being caused to flow from the second externallead terminal to the third terminal via the second terminal and thenonmagnetic base layer, and a second current that is lower than thefirst current being caused to flow to the first terminal.
 2. The headaccording to claim 1, wherein a junction area between the secondmagnetic layer of the second terminal and the nonmagnetic base layer isequal to or more than four times a junction area of the first magneticlayer of the first terminal and the nonmagnetic base layer.
 3. The headaccording to claim 1, further comprising interface layers of anonmetallic high-resistance material disposed between the first to thirdterminals and the nonmagnetic base layer.
 4. The head according to claim1, wherein the first to third terminals are disposed on one face of thenonmagnetic base layer.
 5. The head according to claim 1, wherein thesecond terminal and the third terminal are disposed on one face of thenonmagnetic base layer, and the first terminal is disposed on anotherface of the nonmagnetic base layer.
 6. The head according to claim 1,wherein the first terminal and the second terminal are disposed on oneface of the nonmagnetic base layer, and the third terminal is disposedon another face of the nonmagnetic base layer on an opposite side to thesecond terminal.
 7. The head according to claim 1, further comprising afirst magnetic shield and a second magnetic shield disposed to have thefirst terminal and the nonmagnetic base layer sandwiched therebetween,the first magnetic shield being electrically connecting to the firstterminal, and the second magnetic shield being electrically connected toone of the second terminal and the third terminal.
 8. A magneticrecording and reproducing apparatus comprising: the magnetic headaccording to claim 1; and a preamplifier configured to detect a voltagebetween the first external lead terminal and one of the second externallead terminal the third external lead terminal.
 9. The apparatusaccording to claim 8, wherein the preamplifier detects the voltage by adifferential method.
 10. The apparatus according to claim 8, furthercomprising: a magnetic recording medium: a movement controller thatcontrols movements of the magnetic recording medium and the magnetichead so that they face each other and move relative to each other in afloating state or contacting state; a position controller that controlsa position of the magnetic head to be at a predetermined recordingposition of the magnetic recording medium; and a signal processor thatprocesses a write signal to the magnetic recording medium and a readsignal from the magnetic recording medium using the magnetic head, thesignal processor including the preamplifier.
 11. A method ofmanufacturing a magnetic head comprising: forming a multilayer filmincluding a nonmagnetic base layer, an interface layer of an insulatingmaterial, and a magnetic layer, which are stacked in this order;patterning the multilayer film to form a first portion and a secondportion connected to the first portion, the first portion and the secondportion being arranged along a first direction intersecting with astacking direction of the multilayer film, a width of the first portionin a second direction intersecting with the first direction, and thestacking direction being narrower than a width of the second portion inthe second direction; and patterning the magnetic layer in the firstportion and the second portion to form a first magnetic layer to serveas a magnetization free layer on the interface layer of the firstportion, and a second magnetic layer and a third magnetic layer to serveas magnetization pinned layers on the interface layer of the secondportion.
 12. The method according to claim 11, wherein the secondmagnetic layer and the third magnetic layer are arranged in the firstdirection.
 13. The method according to claim 11, wherein the secondmagnetic layer and the third magnetic layer are arranged in the seconddirection.